1. Field of the Invention
This invention relates to a power converter and more particularly to a power supply which is particularly suitable for use on an aircraft or other vehicle for providing an output of a desired frequency.
2. Description of the Prior Art
Variable speed, constant frequency, power converters are presently in use in many aircrafts. Conventional mechanical to electrical energy conversion as used on most aircraft, ships and vehicles have many limitations such as efficiency, reliability, downtime, maintenance costs and electrical quality. In a prior art variable speed constant frequency generating system a direct drive variable speed generator provides a variable frequency AC output. Thru a static converter package the output from the generator is rectified by a full wave bridge and then filtered to obtain clean DC. The DC is used to power four three phase full wave transistor bridges which are switched on and off to produce precisely timed square waves. Each bridge output is connected to one of four three phase primaries wound onto a single three phase transformer. Two of the primaries are wound in a wye configuration and two are wound in a delta configuration. The magnetic summation of the four bridges produces in the secondary a twenty-four step sinusoidal waveform. The secondary is connected in a wye configuration and produces a single three phase output. The stepped waveform from the secondary windings is then filtered to obtain a clean sine wave. The logic for switching on and off the full wave bridges is digitally derived and based on a stable oscillator to insure an accurate output. Although this DC link approach provides a satisfactory AC output the static converter output package is relatively heavy and the generator system output is restricted to a fixed frequency. The output transformer and filters add significantly to the converter weight.
Electrical devices with switching type output sections, for switching between DC voltages, are known in the art. U.S. Pat. Nos. 3,294,981; 3,351,871; and 4,270,164 are exemplary of these switching type devices.